The Promise of Better Pavement

The world’s two largest full-scale accelerated pavement testing facilities have formed a partnership that promises to benefit state DOTs and thousands of cash-strapped cities and towns who seek economical, durable pavements for their roadways.

By Paul Fournier

Alabama-based NCAT and Minnesota-based MnROAD are sharing resources and expertise under a newly formalized partnership to experiment with similar roadway construction materials under high- and low-volume traffic conditions to determine the effects of climatic differences on pavement performance. Experiment findings are expected to be useful for design of pavements in both warm and cold climates.

The partners each have their own extensive proving grounds, sophisticated testing equipment and highly qualified staff for running experiments on many types of pavements.

NCAT (National Center for Asphalt Technology), headquartered at Auburn University, conducts experiments at their Pavement Test Track in Opelika, Alabama. The 1.7-mile oval track consists of 46 test sections, each 200 feet in length. Sections are sponsored in three-year cycles by state DOT’s, FHWA and industry who all have specific research objectives for their sections and shared objectives for the whole track. NCAT subjects the test sections to two years of continuous trafficking by 70-ton tractor trailers, simulating up to 15 years of Interstate traffic.

The MnROAD pavement testing facility is located approximately 40 miles northwest of Minneapolis. Owned and operated by the Minnesota Department of Transportation, the facility encompasses 3.5-mile interstate (I-94), a 3.5-mile bypass for diverting interstate traffic when needed, and a controlled access 2.5-mile closed-loop, low-volume roadway simulating rural roads. MnROAD has 50 test cells each 400 feet in length. Research is sponsored by state DOTs, Minnesota Local Road Research Board, FWHA and industry.

This is not the first time the two internationally known testing centers have teamed up, according to Dr. R. Buzz Powell, PE, NCAT Assistant Director and Test Track Manager.

“Researchers from NCAT and MnROAD have informally collaborated for years, but now we have a formal agreement covering parallel experiments under an exceptionally broad range of climatic conditions, with funding provided by nineteen state DOTs through the national Transportation Pooled Fund that supports the NCAT Pavement Test Track.”

Current MnROAD-NCAT group experiments focus on two areas, the validation of cracking tests, and the effectiveness of pavement preservation treatments. Treatments at both facilities were designed and built identically, with Dr. Powell overseeing construction of the MnROAD sections by East Alabama Paving, the same contractor that built the NCAT sections.

Dr. Powell explained that the cracking group experiments were undertaken to identify laboratory test methods that predict cracking in the field.

“Hot weather sections were built on the NCAT Pavement Test Track to study near-surface fatigue cracking and cold weather cells were built at the MnROAD facility to study low-temperature cracking. At both facilities, mixes were selected to incorporate various combinations of recycled asphalt pavement (RAP) and recycled asphalt shingles (RAS) and provide a broad range of cracking performance.

The preservation group experiments are being held to measure the effectiveness of preservation treatments and treatment combinations in improving the condition of pavements and in extending their service life for both low- and high-traffic roadways.